The present invention relates to an electro-conductive oxide particle comprising indium atoms, antimony atoms and oxygen atoms or comprising these atoms and zinc atoms, and an electro-conductive oxide particle comprising indium atoms, niobium atoms and oxygen atoms or comprising these atoms and antimony atoms. The electro-conductive oxide particle of the present invention has electro-conductivity and thus is useful as e.g. electro-conductive agents, antistatic agents, electromagnetic wave shielding agents or electric resistance for e.g. plastics, fibers, paper, glass or ceramics.
For liquid crystal displays (LCD) to be used for e.g. display devices of electronic equipment, a transparent electro-conductive thin film is an essential component. As an electro-conductive oxide particle which is a chief material for formation of such a thin film, tin-doped indium oxide (ITO) has conventionally been mentioned first.
JP-A-9-142922 discloses a process for producing an ITO sintered product, which comprises putting a powder mixture containing indium oxide and tin oxide as main components in a mold made of graphite, followed by hot pressing.
Along with various thin film formation techniques, development of more excellent ITO particles has been conducted. Further, methods of coating a coating having ITO particles dispersed therein have been studied in recent years, and ITO particles suitable for these coating methods are also studied actively.
JP-A-8-131815 discloses an indium oxide sol having crystalline indium oxide fine particles containing one or at least two different types of elements selected from the group consisting of Si, Ge, Sn, Zr and Ti, dispersed in water and/or an organic solvent.
Further, JP-A-7-144917 discloses an electro-conductive oxide particle comprising indium atoms, antimony atoms and oxygen atoms in a molar ratio of In:Sb:O of 1:0.02-1.25:1.55-4.63. It also discloses an electro-conductive oxide particle having a molar ratio of In:Sb:O of 1:0.83-1.25:3.58-4.63 and having a crystal structure of indium antimonate, and an electro-conductive oxide particle having a molar ratio of In:Sb:O of 1:0.02-0.10:1.55-1.75 and having a crystal structure of indium oxide.
It was found that the above-described indium antimonate when press-molded under a pressure of 300 kg/cm2 exhibits a good electro-conductivity with a specific resistance of 10 xcexa9cm, however, it is possible to further improve the electro-conductivity.
It is an object of the present invention to provide an electro-conductive oxide particle having an excellent electro-conductivity and useful for coating methods also, by studying e.g. molar ratio of antimony and indium and production process.
Further, it was found that niobium can be used instead of antimony. It is an object of the present invention to provide an electro-conductive oxide particle having an excellent electro-conductivity and useful for coating methods also, by studying e.g. molar ratio of niobium, antimony and indium and production process.
According to a first aspect of the present invention, there is provided an electro-conductive oxide particle comprising indium atoms, antimony atoms and oxygen atoms in a molar ratio of Sb/In of from 0.03 to 0.08, having a primary particle diameter of from 2 to 300 nm, and having a crystal structure of indium oxide.
According to a second aspect of the present invention, there is provided an electro-conductive oxide particle comprising indium atoms, antimony atoms and oxygen atoms in a molar ratio of Sb/In of from 0.04 to 0.06, having a primary particle diameter of from 2 to 300 nm, and having a crystal structure of indium oxide.
According to a third aspect of the present invention, there is provided an electro-conductive oxide particle comprising indium atoms, antimony atoms, zinc atoms and oxygen atoms in a molar ratio of Sb/In of from 0.03 to 0.08 and in a molar ratio of Zn/Sb of from 0.02 to 2.50, having a primary particle diameter of from 2 to 300 nm, and having a crystal structure of indium oxide.
According to a fourth aspect of the present invention, there is provided an electro-conductive oxide particle comprising indium atoms, niobium atoms and oxygen atoms in a molar ratio of Nb/In of from 0.01 to 0.10, having a primary particle diameter of from 2 to 300 nm, and having a crystal structure of indium oxide.
According to a fifth aspect of the present invention, there is provided an electro-conductive oxide particle comprising indium atoms, niobium atoms and oxygen atoms in a molar ratio of Nb/In of from 0.03 to 0.08, having a primary particle diameter of from 2 to 300 nm, and having a crystal structure of indium oxide.
According to a sixth aspect of the present invention, there is provided an electro-conductive oxide particle comprising indium atoms, niobium atoms, antimony atoms and oxygen atoms in a molar ratio of (Nb+Sb)/In of from 0.01 to 0.10 and in a molar ratio of Sb/(Nb+Sb) of from 0.01 to 0.99, having a primary particle diameter of from 2 to 300 nm, and having a crystal structure of indium oxide.
According to a seventh aspect of the present invention, there is provided the electro-conductive oxide particle according to any one of the first to sixth aspects, which is a stick particle having an aspect ratio of from 2 to 10.
According to an eighth aspect of the present invention, there is provided a process for producing the electro-conductive oxide particle as defined in any one of the first to sixth aspects, which comprises calcining a composition selected from the group consisting of a mixture of an In compound and an Sb compound, a mixture of an In compound, an Sb compound and a Zn compound, a mixture of an In compound and a Nb compound, and a mixture of an In compound, a Nb compound and an Sb compound, in the air at a temperature of from 500 to 900xc2x0 C.
According to a ninth aspect of the present invention, there is provided a process for producing the electro-conductive oxide particle as defined in any one of the first to sixth aspects, which comprises calcining a composition selected from the group consisting of a mixture of an In compound and an Sb compound, a mixture of an In compound, an Sb compound and a Zn compound, a mixture of an In compound and a Nb compound, and a mixture of an In compound, a Nb compound and an Sb compound, in the air at a temperature of from 500 to 900xc2x0 C., followed by reducing calcination in an atmosphere comprising hydrogen and nitrogen in a volume% of 2xe2x88x9d100:98-0 at a temperature of from 80 to 450xc2x0 C.
According to a tenth aspect of the present invention, there is provided a process for producing the electro-conductive oxide particle as defined in any one of the first to sixth aspects, which comprises contacting a composition selected from the group consisting of a mixture of an In compound and an Sb compound, a mixture of an In compound, an Sb compound and a Zn compound, a mixture of an In compound and a Nb compound, and a mixture of an In compound, a Nb compound and an Sb compound, with an alkali compound in an aqueous medium to form a slurry of indium hydroxide doped with at least one metal element, washing and drying the slurry and calcining it in the air at a temperature of from 500 to 900xc2x0 C.
According to an eleventh aspect of the present invention, there is provided a process for producing the electro-conductive oxide particle as defined in any one of the first to sixth aspects, which comprises contacting a composition selected from the group consisting of a mixture of an In compound and an Sb compound, a mixture of an In compound, an Sb compound and a Zn compound, a mixture of an In compound and a Nb compound, and a mixture of an In compound, a Nb compound and an Sb compound, with an alkali compound in an aqueous medium to form a slurry of indium hydroxide doped with at least one metal element, washing and drying the slurry and calcining it in the air at a temperature of from 500 to 900xc2x0 C., followed by reducing calcination in an atmosphere comprising hydrogen and nitrogen in a volume % of 2-100:98-0 at a temperature of from 80 to 450xc2x0 C.
According to a twelfth aspect of the present invention, there is provided a process for producing the electro-conductive oxide particle as defined in the seventh aspect, which comprises contacting a composition selected from the group consisting of a mixture of an In compound and an Sb compound, a mixture of an In compound, an Sb compound and a Zn compound, a mixture of an In compound and a Nb compound, and a mixture of an In compound, a Nb compound and an Sb compound, with an alkali compound in an aqueous medium at a temperature of from 0 to 10xc2x0 C. to form a slurry of indium hydroxide doped with at least one metal element, washing and drying the slurry and calcining it in the air at a temperature of from 500 to 900xc2x0 C.
According to a thirteenth aspect of the present invention, there is provided a process for producing the electro-conductive oxide particle as defined in the seventh aspect, which comprises contacting a composition selected from the group consisting of a mixture of an In compound and an Sb compound, a mixture of an In compound, an Sb compound and a Zn compound, a mixture of an In compound and a Nb compound, and a mixture of an In compound, a Nb compound and an Sb compound, with an alkali compound in an aqueous medium at a temperature of from 0 to 10xc2x0 C. to form a slurry of indium hydroxide doped with at least one metal element, washing and drying the slurry and calcining it in the air at a temperature of from 500 to 900xc2x0 C., followed by reducing calcination in an atmosphere comprising hydrogen and nitrogen in a volume % of 2-100:98-0 at a temperature of from 80 to 450xc2x0 C.
According to a fourteenth aspect of the present invention, there is provided a process for producing the electro-conductive oxide particle as defined in the seventh aspect, which comprises contacting an aqueous medium containing a composition selected from the group consisting of a mixture of an In compound and an Sb compound, a mixture of an In compound, an Sb compound and a Zn compound, a mixture of an In compound and a Nb compound, and a mixture of an In compound, a Nb compound and an Sb compound, with a heat resistant strongly basic ion exchange resin, followed by heating at a temperature of from 40 to 100xc2x0 C. to form a slurry of indium hydroxide doped with at least one metal element, drying the slurry and calcining it in the air at a temperature of from 500 to 900xc2x0 C.
According to a fifteenth aspect of the present invention, there is provided a process for producing the electro-conductive oxide particle as defined in the seventh aspect, which comprises contacting an aqueous medium containing a composition selected from the group consisting of a mixture of an In compound and an Sb compound, a mixture of an In compound, an Sb compound and a Zn compound, a mixture of an In compound and a Nb compound, and a mixture of an In compound, a Nb compound and an Sb compound, with a heat resistant strongly basic ion exchange resin, followed by heating at a temperature of from 40 to 100xc2x0 C. to form a slurry of indium hydroxide doped with at least one metal element, drying the slurry and calcining it in the air at a temperature of from 500 to 900xc2x0 C., followed by reducing calcination in an atmosphere comprising hydrogen and nitrogen in a volume % of 2-100:98-0 at a temperature of from 80 to 450xc2x0 C.
Now, the present invention will be described in detail with reference to the preferred embodiments.